But when a woman assistant tried to stop him leaving the premises he produced the weapon and pointed it at other customers before making his escape.

Checkley, a drug addict for 14 years, admitted theft, assault and possessing an offensive weapon and he was told by Recorder Shamin Qureshi prison was the only appropriate sentence.

"You are a typical drug addict and you cannot say you have not been given chances by courts in the past.

"There is a great deal of public concern at the moment about knives and, on this occasion, it was fortunate you did not use it to cause injury. "But a young girl working in the shop was put in fear of getting stabbed or even killed."

Timothy Sapwell, defending, told the court it was the "depresssingly familiar" story of a life being ruined by an addiction to Class A drugs.